Australia, known for its spectacular natural beauty, also has many spectacular water filled caves and sinkholes. Since the 1950s many visiting divers are attracted by the "air-clear" water conditions experienced in the sinkholes and caves found in the Lower South East (now called the Limestone East) of Southern Australia. Until the mid 1980s divers generally relied on single diving cylinders, homemade torches, and reels, but mixed-gas and rebreather technologies have made it possible to expand explorations. This area is generally know within the cave diving community as the Mount Gambier region. As incredible as cave diving is, it is a dangerous sport to pick up so proper training and precaution must be taken. The Cave Divers Association of Australia (CDAA) is the major cave diving organization in Australia and is responsible for the administration of cave diving at many sites. The CDAA was created after a series of incidents between 1969 and 1974 in the Limestone East in which 11 divers died (including a triple and a quadruple fatality). Since then a testing system and training system (the latter replacing the former), which consists of 3 levels of qualification - Deep Cavern, Cave, and Advanced Cave, have helped reduce the fatality rate. Since 1974, there have been 5 diving deaths. All cave diving in the Limestone Coast as well as at some New South Wales sites and the Nullarbor requires divers to be members of the CDAA, whether in the capacity of a visitor or a trained and assessed member. A number of other organizations participate in cave diving activities within Australia. The Australian Speleological Federation Cave Diving Group, which was formed in 2005, coordinates projects focused on exploration and mapping at sites throughout Australia. Diving training courses in various aspects of cave diving are offered by a variety of organizations: Global Underwater Explorers, International Association of Nitrox and Technical Divers and Technical Diving International. During the 1980s, the Nullarbor Plain was recognized as a major cave-diving area, with one cave, Cocklebiddy, being explored for more than 6 kilometres. Said explorations involved the usage of large sleds to which were attached numerous diving cylinders and other paraphernalia, and which were then laboriously pushed through the cave by the divers. In more recent years divers have been utilizing compact diver-towing powered scooters, but the dive is still technically extremely challenging. Over the past 20 years, a number of other very significant caves have also been discovered, such as the 10+ (Lineal) kilometre long Tank Cave near Millicent in the Limestone Coast, other very large features on the Nullarbor, and the adjacent Roe Plain. Likewise the Australian cave diving community utilizes many techniques, equipment, and standards used internationally.